Stellar convective stability

Stellar convective stability compares the density of an adiabatically displaced fluid element with its new surroundings. Temperature and composition gradients determine whether buoyancy restores the element or amplifies its displacement.

For uniform composition, a stellar layer is convectively stable when $\nabla <{\nabla }_{\mathrm{ad}}$ and unstable when $\nabla >{\nabla }_{\mathrm{ad}}$, where $\nabla =d\log T/d\log P$.

With a composition gradient, stability requiresA mean molecular weight increasing inward normally provides an additional stabilizing term.

A convective core is a central stellar region in which the radiative temperature gradient exceeds the adiabatic threshold. Efficient convection makes its entropy nearly uniform and mixes its composition.